Conventionally, in general, as one of c-BN based sintered cutting inserts, a type of c-BN based sintered cutting insert is known which includes a sintered compact made of cubic boron nitride based ultra-high pressure sintered material (hereinafter referred to as c-BN based material), the sintered compact substantially exhibiting a two-phase structure having a continuously bonded phase and a hard dispersed phase when observed using a scanning electron microscope, and including 20 to 45 wt % at least one component as the continuously bonded phase selected from titanium nitride (hereinafter referred to as TiN), titanium carbonitride (hereinafter referred to as TiCN), and titanium carbide (hereinafter referred to as TiC), and, as the balance, cubic boron nitride (hereinafter referred to as c-BN) as the hard dispersed phase, as disclosed, for example, in Japanese Unexamined Patent Application, First Publication No. Sho 53-77811, and moreover, it is also known that such c-BN based sintered cutting inserts are used, for example, for performing surface finish cutting of various steels and cast irons.
On the other hand, in recent years, cutting apparatuses tend to have significantly high performance and high power, and in addition, it is strongly demanded that cutting operations be performed with less power and less energy; therefore, cutting operations tend to be performed at high speed. However, when the above-mentioned conventional c-BN based sintered cutting inserts or other type of c-BN based sintered cutting inserts are used for performing finish cutting of a difficult-to-machine material, such as high-hardened steel, at high speed, a c-BN phase, which is a hard dispersed phase substantially corresponding to TiCN forming a continuously bonded phase, tends to be separated due to insufficient adhesion of the c-BN phase. As a result, the cutting edge tends to chip (i.e., to have micro-breakage), which leads to a relatively short operation life.